search

google / OpenSK

OpenSK is an open-source implementation for security keys written in Rust that supports both FIDO U2F and FIDO2 standards.
Apache License 2.0
3k stars 291 forks source link

OpenSK and ECDAA #475

Closed geo-lit closed 1 year ago

geo-lit commented 2 years ago

Hi I was in contact with @jmichelp asking him about ECDAA.

Just wondering if anyone knows why the draft has not been implemented, and has been stagnant since 2018 (although I recently found a new draft from FIDO from May 2021 https://fidoalliance.org/specs/common-specs/fido-ecdaa-algorithm-v2.1-rd-20210525.pdf) I know that it's not in the specification, but seems like it would solve any privacy issues that come with batch attestation, which is not 100% private.

Also looking on guidance in terms of how I could start it's implementation using OpenSK. I tried familiarizing myself with the repo, but am a bit lost, so any guidance would be appreciated, specifically attestation flow, and where ECDAA would be added from the program-flow perspective.

kaczmarczyck commented 2 years ago

I don't expect widespread usage of ECDAA. I think the underlying cryptography is relatively young, i.e. the 2021 draft fixes security holes from 2018. At the moment, I recomment to solve attestation related privacy issues by simply not using batch attestation. This is the default in OpenSK. It might fail for some websites with strict policies, but I don't expect OpenSK to be on their whitelists anyway. I'd argue that ECDAA's additional complexity is not worth the marginal benefit. Without attestation already, security keys are a better second factor than most.

That is for our product decision on ECDAA on OpenSK. However, from a research perspective, I welcome anyone to implement and experiment with it. A few thoughts and pointers:

  1. In case of expected binary size increases, its code should be behind a feature flag.
  2. All cryptography can be added to our software library. The EC basics are already there, for ECDSA and ECDH.
  3. Batch attestation, if enabled, is set in process_make_credential here. It should give you some ideas about how to replace it with a different mechanism.

Feel free to tell me more about where exactly you're lost or ask more concrete questions, then I can give you a better answer where to look.

kaczmarczyck commented 1 year ago

There are no new developments around ECDAA, so I assume no interest. Please reopen when this changes.